"Metal handles feel colder than wooden ones at the same temperature because metal pulls heat away from your skin quickly, while wood lets heat leave slowly." The author's purpose in this passage is to

"1. Fill the cup to the marked line. 2. Drop in one paper clip. 3. Mark the new water level. 4. Repeat with a second clip and mark again." The author includes these numbered directions in order to

"We planted six seeds in dark soil and six in sandy soil, watered both trays the same, and after two weeks the dark-soil tray had five sprouts and the sandy tray had two." The author's purpose here is to

"3. Pour the hot water slowly. Keep the thermometer off the bottom of the cup, or the reading will follow the glass rather than the water." The second sentence is included mainly to

"Bridges have small gaps at each end. Metal expands in summer heat, and without the gaps the growing beams would push against each other and buckle." The writer includes the second sentence to

A lab report ends, "The sample's temperature rose four degrees in ten minutes." The author includes this sentence to

"Ice floats because water spreads into an open pattern as it freezes, so a block of ice takes up more room than the same water did as a liquid." The author's purpose in this passage is to

"To test a rock for chalk, place one drop of vinegar on a dry spot. Watch for thirty seconds. Bubbles mean the rock holds chalk; no bubbles means it does not." The author's purpose in these directions is to

"Each of the three fans ran for one hour beside the same wet cloth. The cloth by the strongest fan dried first, the middle fan second, and the weakest fan's cloth stayed damp." The author's purpose here is to

A set of directions opens, "Before you begin, gather a ruler, a rubber band, two pencils and a sheet of graph paper." The author includes this opening sentence to

After the sixth trial a report adds, "The data suggest the slower melting was caused by the foil wrapper, since only that variable changed." The author includes this sentence to

A report ends, "The researchers may have hoped that the new coating would last a full year." The author includes this sentence to

"Sound travels faster through steel than through air because the particles in steel are packed close together, so a push passes from one to the next almost at once." The author's purpose in this passage is to

"1. Tape the mirror upright. 2. Shine the flashlight at it from the left. 3. Mark where the light lands on the wall. 4. Move the flashlight one hand-width right and mark again." The author prints these steps to

"We dropped the same ball from waist height onto tile, carpet and grass, ten drops each. It bounced highest on tile every time and lowest on grass in nine of ten drops." The author's purpose here is to

A set of directions ends, "Repeat step 3 two more times and average your three readings." The author includes this sentence to

An article explains blood flow, then adds, "A narrowed vessel acts like a pinched garden hose: the same amount must pass through a smaller opening." The author includes this sentence to

A field report states, "Twelve of the twenty nests held eggs." The author includes this sentence to

"Salt lowers the temperature at which water freezes, so scattering it on a road keeps a thin film of liquid on the surface instead of a sheet of ice." The author's purpose in this passage is to

"Hold the leaf flat against the paper. Rub the crayon sideways over it until the veins show. Do not press hard, or the paper will tear before the pattern appears." The author's purpose in this passage is to

"We left identical apple slices in four spots. After one day the slice in the sealed jar was pale, the two on the counter were brown, and the one in the freezer looked unchanged." The author's purpose here is to

Step 5 of a procedure reads, "Unplug the hot plate before you lift the pan." The author includes this sentence to

An article on tides pauses to say, "A spring tide is a tide with the widest gap between high and low water. It has nothing to do with the season." The author includes this sentence to

A study ends, "Because the count fell in all six ponds and only the water temperature changed, the warming most likely drove the decline." The author includes this sentence to

"A plant leans toward a window because the cells on the shaded side grow longer than those in the light, and the longer side bends the stem the other way." The author's purpose in this passage is to

"Weigh the empty cup and write the number down. Add the sand, weigh again, then subtract the first number from the second." The author's purpose in this passage is to

"Two groups of ten students read for twenty minutes, one group in a quiet room and one with music playing. The quiet group answered more questions correctly on the same short test." The author's purpose here is to

A step in a procedure reads, "Add exactly three drops of dye, no more." The author includes the words "no more" to

A report opens, "We wanted to find out whether a wider paper wing keeps a glider in the air longer." The author includes this sentence to

A weather article closes, "Perhaps future storms will follow the same track, though no record yet shows one that did." The author includes this sentence to

"Damp clothes on a line dry faster on a breezy day because moving air carries away the water that has just left the cloth, leaving room for more to escape." The author's purpose in this passage is to

"Lay the seed on wet cotton in the lid, close the box, and set it on a shelf away from the window. Open it each morning and add water until the cotton is damp again." The author's purpose in this passage is to

"We coated one nail with wax, one with oil, and left one bare, then set all three in water for a week. The bare nail rusted, the oiled nail showed a few spots, and the waxed nail stayed clean." The author's purpose is to

An explanation of how bees carry pollen ends, "Without that transfer, many of the fruits on a lunch tray would never form." The author includes this sentence to

A step reads, "Use the ruler marked in millimeters, not the plain one." The author includes this instruction to

A report states, "The trial ran for six days, and the meter was read at noon each day." The author includes this sentence to

"A crack in a sidewalk widens each winter because water seeps in, freezes and pushes outward as it turns to ice, then melts and lets still more water in." The author's purpose in this passage is to

"Cut two slits in the tube, slide the card into them, and check that the card sits square. If it leans, pull it out and widen the lower slit slightly." The author's purpose in this passage is to

"Three cups of water sat in the sun, one covered with clear wrap, one with foil, one left open. After four hours the open cup had lost the most water and the covered cups had lost almost none." The author's purpose is to

A report notes, "Only one class was tested, so the result may not hold for older students." The author includes this sentence to