Helium is used in balloons because it is

The combining of one substance with another to yield a different product is the result of a (n): A: physical change B: chemical change C: phase change D: exothermic change

A baseball is thrown directly upward from ground level with a velocity of + 15 m/s. What are the two times when the ball is 10 m above ground level? Take acceleration due to gravity to be - 9.8 m/s^2.

Where do seasons alternate between a very dry season and a monsoon season, with a stable warm climate? tropical rainforest taiga desert savanna

A spherical shell of radius 9.0 cm carries a uniform surface charge density σ = 9.0 nC/m2. The electric field at r = 9.1 cm is approximately

A particle of mass 5kg is pulled along a rough horizontal surface by a string which is inclined at 60° to the horizontal.

Which of these is not a source of the shock waves that lead to protostars?

Which kind of information is known about a person if that person's DNA is in a database? A. how old the person is B. where the person was probably born C. some diseases the person might have D. whether the person is likely to commit a crime

A science teacher ran a marathon. After the race she showed her students the silver blanket she was given to keep her warm. A group of students investigated how the colour of the blanket affected how much infrared radiation is absorbed

Students asked to measure the temperature of a reaction beaker recorded the following temperatures. 103.7°C, 108.4°C, 105.8°C, 104.6°C The actual temperature is 105.1°C. Which measurement is the most precise

Two atoms that are isotopes of one another must have a different number of what? electrons neutrons protons all particles