What is a chemical combination of substances

A) a compound

B) an atom

C) a mixture

D) an element

The acceleration of the universe's expansion is attributed by many cosmologists to the presence of which of the following? A. Dark matter B. Black Holes C. Dark energy D. Gravitaional pulls from unseen galaxies** i think its D but not sure

Which of the following is an example of a chemical change? Boiling water Burning paper Dissolving sugar in water Melting gold

Jessica took a mylar balloon outside on a very hot day. As she waited for the bus the balloon began to get bigger.

You notice that you always get sleepy right after lunch. What part of the scientific process are you performing by noticing this?

A rock is thrown straight up and passes by a window. The window is 1.7m tall, and the rock takes 0.19 seconds to pass from the bottom of the window to the top. How far above the top of the window will the rock rise?

A boulder on top of a cliff has a potential energy of 12400J. How high above is the boulder?

If the graph represents speed what is measured on the x and y axes

It is difficult to lift a heavy stone than the lighter one on the earth, why?

The vapor pressure of ethanol at 25 degrees C is 7.83 kPa. Calculate the vapor pressure in atm. Round answer to 3 significant digits.

According to Newton's second law of motion acceleration or an object depends upon the ___ of the object and the ___ Acting on it. I'm confused on what the blanks are. I can't find them.